Muffler as used with equipment such as tractors, trucks, bulldozers, and the like have a resonant frequency during engine operation that varies with engine speed and load. It is important that the resonant frequency of the muffler be different from that of the vibrational frequency of the operating equipment itself, otherwise harmonic vibrations could be set up in the muffler which could substantially reduce the life of the muffler. To overcome this potential problem, muffler designs should be tested with the operating equipment or on a shaker for the purpose of determining the vibrational frequency of the muffler under varying operating conditions.
Accelerometers are used to measure the acceleration of moving bodies. However, mufflers have an outer body temperature generally in the range of 800.degree. F. to 1200.degree. F. during operation. Although accelerometers have been designed with special material to be used in environments up to 670.degree. F., a conventional accelerometer cannot be used with a muffler at the muffler operating temperature.
Therefore, there has been a need to develop a device which could measure the vibrational characteristics of equipment, such as an exhaust muffler, that operates at high temperatures.